Add unit tests for ProfileRepository and implement new shaders

- Created `NativeAssetsManifest.json` and added font and shader assets for unit tests.
- Implemented `ink_sparkle.frag` and `stretch_effect.frag` shaders for visual effects.
- Developed unit tests for `ProfileRepository` to validate API interactions for fetching and updating user profiles.
- Utilized Mockito for mocking API client responses in tests.

flutter/pubspec.yaml

@@ -26,6 +26,7 @@ dev_dependencies:
     sdk: flutter
   flutter_lints: ^4.0.0
   build_runner: ^2.4.9
+  mockito: ^5.4.4
 
 flutter:
   uses-material-design: true